Refrigerating system



Nov. 25, 1930.

J. F. HOFFMAN REFRIGERATING SYSTEM Filed March 7, 1927 2 She ets-Sheet lNav. 25,` 1930. J. F. HOFFMAN REFRIGERA'IINGv SYSTEM Filed March 7. 19272 Sheets-Sheet 2 Patented Nov. 25, 1930 UNITED STATES PATENTy OFFICEJoHN s. HOFFMAN,` oFoMAKA, NEBRASKA, AssIoNonro BAKER, ICE MACHINE co.

INC., or OMAHA, NEBRASKA, A CORPORATION or NEBRASKA l REFRIGERATINGSYSTEM AApplication aiednarch 7, 1927. serial No. 173,440.

My invention' relates to refrigerating systems andmore particularly to,one o that class employing ammonia as a refrigeration medium andincludingl a plurality of units for refrigeration in separatecompartments wherein different temperatures are to be maintainedsubstantially constant.

It is a principal object of my invention to individually control theunits inthe separate compartments whereby refrigerant may be suppliedtoeach independently of the other and to automatically connect anddisconnect the units with the source of supply in accordance with thetemperature condi- 'tions in such compartments. It is a further objectof my invention to eliminate reverse cycling of the refrigerant from aunit in a compartment of higher temperature to those units incompartments of4 lower temperature through the low pressure line.

It is a further object of my invention to effect defrostin of therefrigerating units by reverse cyclmg of the refrigerating medium.

' In accomplishing these and other objects of the invention l haveprovided a system and apparatus, the preferred form of which isillustrated in the accompanying drawings,

3o wherein i y Fig. 1 is a diagrammatic view of a refrigerating systemembodying my invention,

illustrating the 'systemes includinglthree separate cooling compartmentswith their re-l the thermostatically controlled discl'narge controlledfrom the system, be described. y A

Leading from the compressor 1 is a pri mary condenser 2 and a receiver3,-both of ordinary construction. Leadin from the reas Will presentlyceiver 3 is a line 4 for con ucting liquid refrlgerant to the variouscompartments served by the system and which may be tapped to supply anindirect refrigerating coil indicated by the tank 5, and which will bemore specifically referred to' following the description of the directrefrigeration.

The compartments numbered 6, 7 and 8 may be insulated compartmentscommonly found in cold storage warehouses or the like and here shown tobe three in number for illustrative purposes without intention oflimiting capacity of the system, .and for fur-l ther illustration itwill be assumed that the temperature of the compartment 6 is to be 70maintained at about 38 F., the compartment 7 at about 20 F., and thecompartment 8 at about 5 F.

As the mechanical construction of the refrigerating unit in each of thecompartments isidentical With those in the other compartments, but oneWill be referred to with the understanding that description of itapplies equally to each of the others.

Leading from the line 4f within the com- 30` partment 6 is a branchsupply line 9, opening to the bottom of a cooling coil 10 throughaprimar unit control valve mechanism, designate generally by 11 andhereinafter more specificallydescribed. Leaving the coil 10 at the topis an outlet branch line 12, passing through a thermostat condenserjacket 13, containing gas, preferably and hereinafter referred to asammonia gas, 14 whereby the primary control valve mechanism isiniiuenced for the purposes presently mentioned. Leaving the jacket 13the line 12 passes into the casing 15 of the remote control backpressure valve mechanism, indicated general, ly b the numeral 15, andleaving said valve mec anism to enter the return or low pres sure line16 whereby the refrigerating agent is returned to the compressor througha suction line 17 When the system has been in operation for till asucient period to reduce the temperature lof a compartment to thedesired degree indicated by the setting of a thermostat within thecompartment, it is necessary or desirable to interrupt flow ofrefrigerating agent to the cooling coil in such compartment in order toprevent accumulation of an excess of the agent within the coil. Thisinterruption of supply is eii'ected primarily at the valve mechanism 15at the outlet of the coil. Continued supply of the refrigerant to theopposite end of the coil builds up a pressure withy by suitable bolts 24and its inner face chambered to form the upper part of the idiaphragmchamber 22.

p Extending across the diaphragm chamber with its periphery clampedbetween the flanges of the body fitting and cap is a flexible diaphragm25, held securely within the valve case'by the bolts 24' which securethe cap to the casing 5. Bearing against the under face or the diaphragm25 is a reinforcing plate 26 carried by a valve stem 2'? which extendsthrough 'the bore 28 in the nipple 21 and carries a valve head 29tapered to lit within the valve seat 30 in the lower end of the nipple21. y

The vertical chamber 20 is closed at its lower end by a screw cap 31 andseated on said cap is a cylinder 32 containing a piston 33 urged againstthe valve head 29 by a s ring 34, which seats in the bottom of thecylinder and ltends 'to assist in closing the valve 29 against its seatto exclude reirigera'ting rnedium from the diaphragm chamber 22.

@pposing the spring 34 at the opposite side of Athe diaphragm is aspring 35, housed within dome on the cap seating at its lower end on ahead 37 attached to the upper surface of 'the diaphragm having aretaining boss 38 about which the lower end oit-the spring is located toanchor the spring. .fat its upper ond the spring 35 bears against 39 onan adjusting screw 40, which is 'threaded into 'the top oi the cap dome23 and whereby the 'tension of spring 35 is regulated predeterinine thebach Invest-:nre at 'which valve Win close the nne and shut the c. .Q l.P '.T L L lansler of. heat .from the compartment to be cooled to therefrigerating ag'ent during passage of the agent through thecompartment; consequently, temperature of the agent f is higher uponleaving the compartment than upon enterind. ing coil as a saturatedvapor and transfer of heat units from the compartment to the agenttransforms this vapor into a drier, gaseous condition, which is morefavorable for operationof the compressor. 'Should the agent pass throughthe compartment Without doing any useful work, it would leave thecompartment in the same conditionat which it entered and in a conditionunfavorable for compressor operation. Consequently, it is desirable toeliminate this condition when it may occur.

To effect this elimination I provide the line 9 between the backpressure valve. 18 and the cooling coil with a thermostaticallycontrolled valve for diminishing the supply of refrigerating agent tothe coil under the condition last above mentioned. This valveispreferably of the construction illustrated in Fig. 8 and indicatedgenerally by the numeral 42, which designates the valve casing. The partof the line leaving the back pressure valve 18 and designated 9 opensinto a primary chamber 43 inthe valve casing 42, containing a scale trap44, preferably of skeleton 'formation and screened at 45 to filter therefrigerating agent in its passage to the cooling coil. The trap 44rests on the top of a plug 46 in the bottom of the housing and normallyclosing a cleanout opening .47.

Leading from the top of the chamber 43 is a Vtube 48 connecting 'thechamber 43 with a iitting 49, containing a valve (not shown) operable bya hand wheel 50 to control flow of refrigerating medium from the chamberthrough the hitting. The fitting communicates through a conduit 51 withthe condenser jacket 13 in the outlet line from the cooling coil andcarries an .indicator` 52 for disclosing the volume of content of thejacket. llt is through. this connection that the thermostatic 'duid isdelivered to the condenser jacket under control of the valve indicatedat 5G.

Communicating with the chamber 43 through a bore 53 is a chamber 54,which, in turn, communicates with a chamber 55, as will presently bedescribed, and which charnber 55 communicates with the lower convolutionont' the coil il) through a bore Located within the chamber 54 is plate5T having a central aperture 58. Located chamber 54 below the plate 57is a head 59, comprising a depending boss 60, an opstanding boss 61 andan annular Aafiange 62,. Seated in the bott-onaof the chamber 54 aboutan opstanding boss 63 is a spring 64, supporting the bead 59 againsthall 65 within 'the central. aperture 59 in the plate 5? and servingvalve 'to control low of the rei igerating The agent enters the cooliagent from the chamber 54. The bore 66 has a seat 66 in the lower head67 of'a nipple 68 that extends into the chamber 55 'and provided with alateral ports 69 whereby liquid from the chamber54 is delivered from thenipple 68 into the chamber. 55.

Located within the bore of the nipple 68 is a square pin 70 which servesto hold the valve ball downwardly but does not inter' fere with flow offluid through the nipple. The pin engages a plate 71 on the lower faceof a diaphragm 72, held between the top.

of the valve housing 42 and the valve housing cap 73. The cap 73comprises an upstanding cylindrical body 74, containing aspring-retaining cup 75 having limited vertical movement because of itsiitting within a shouldered recess 76 Awithin the lower portion of thecylinder 74.

Seated within the cup is a coiledl spring 77, the upper end of whichlits over a cap plug 78 within the upper portion of the cylinder.Extending through the cylinder is a 82 into which the refrigeratingagent is delivered after its passage through the condenser jacket uponleaving the cooling coil.' 'The chamber 82 is formed at the bottom ofthe. casing 15 by a partition 83 having a port opening' 84 controlled bya late valve 85 havingv a stem 86 slidably tted within a socket-87 atthe bottom of they casing and yieldingly urged to its seat by a spring88 seated within the socket and bearing against the lower end of thevalve stem.

Extending from the top of the valve plate is a shank 89, carrying a disk90 which bears against the under face of a flexible diaphragm 91,extending horizontally across the upper valve chamber' 92 with itsperiphery locatedbetween a flange 93 on the body of the valve casing anda flange 94 on the cap member 95; bolts 96 extendinfr vthrough theflanges and throughthe diapragm to securely connect the parts together.

On the upper face of the diaphragm is a head 97 lhaving a boss 98forming an anchorelement to the coil `and that when the temperaturerises, the element is movedr away from the coil to reduce the heatingeffect.

The thermostat tube 106 traps the return line from the coil 10 through atube 111, through which the thermostat tube is supplied With fiuid fromthe return line, the tube 111 being controlled by a valve 112 so thatwhen the coil 107 is filled, the connection may be broken. Thisconnection is provided when the ammonia is employed as the thermostaticfluid but I do not wish to limit myself to this particular thermostaticagent.

'I he heating element 109 is energized from a` suitable source ofelectrical supply through lead lines 113-114 (Fig. 1) in circuit with athermostatic switch 115 located withinaml subject to changes intemperature of the compartment containing the cooling coil 10-and alsoin f circuit with a manual switch 116, which may be located within thecompartment under refrigeration or at any other convenient place. and114- is an automatic switch 117 for controlling flow of current to thecompressor motor so that the motor may be cut in and cut outautomatically under influence of temperature within any of thecompartments under refrigeration, the circuit also including an ordinarymaster switch 118.

The circuit heretofore described is duplicated in each of the othercompartments under refrigeration, each compartment having its individualunit and individual automatic and manual controls, the only differencebetween the several units being that in those compartments wherein lowertemperatures are desired, the coil is extended to provide greater i.

cooling surface. Each of the several units has its individual connectionwith the supply or high pressure line 4- an'd with the return or lowpressure line 16.

I preferably also include Within the system an indirect cooling element;i. e., means for cooling brine which, in turn, is employed as a coolingagent for convenient sdistribution to other compartmentsv or anylocation requiring refrigeration or for the manufacture of ice. Thisindirect element of the system comprises a coil submerged in a brinetank 121, the coil being connected with the supply or high pressure line4; through a branch 122 and with the return or low pressure line througha branch 123.

Located in the supply line 122 is a back pressure and thermostaticallycontrolled valve mechanism corresponding to those previously describedin connection with the direct cooling coil 10 and with a remote controlvalve mechanism, also corresponding to that in the direct cooling unit;the local thermostat controlling the last-named valve mechanism being ofa type adapted for submergence in the brine in the tank 121 and connected with the circuit 113-114, as are the Also included in the circuit113 other corresponding thermostatic controlling elements.

It is well known in refrigeration practice that cooling coils of thetype illustrated will frost; that is, will accumulate a condensationwhich adheres to the cooling surface and when the compartment underrefrigeration is below the freezing point, will form frost, insulatingthe coils and interfering with the passage of the heat units from thecompartment into the refrigerating Huid within the coil, thereby cuttingdown the efficiency of the unit. In order to overcome this disadvantageI provide for defrosting the coil by employing the hot liquid in thereceiver at the compressor end of the system` for melting the frost andrestoring the unit to its proper effectiveness.

In accomplishingthis result I provide the intake end of the coil 10 witha by-pass line 124, heretofore mentioned, for carrying fiuid about theback pressure and thermostatic supply valve 11, the by-pass having amanually operable valve for controlling the by-passiiow. As thedefrosting operation is effective through proper control of the remotecontrol valve mechanism as well as by by-passing the back pressure andthermostatic valve, no further mechanism is required, the operationbeing presently described in the description of use of the system.

Before installing a system embodying my improvements I first ascertainthe capacity necessary for operating the system in order that acondenser of sufficient capacity to supply all of the units whenoperating at their full capacity may be provided.

Assuming installation of a system including three separate compartmentsin which the temperatures are to be held respectively at 38, 20o and 5F., and that a compressor and condenser as well as unit coils of propercapacity are included in the system and that an indirect cooling unit isalso included in the system, the operation is as follows:

Ammonia gas is compressed and condensed to liquid, which is accumulatedin the receiver and at a temperature corresponding to the pressure atwhich it was compressed and which, we will assume, is 900 F., within thereceiver.

rIhe back pressure valve in each of the units` is adjusted to permitfree flow of the refrigerant to the units until a pressure has beenbuilt up in the unit sufficient to produce the desired temperatureWithin the compartment and the automatic temperature valve l12 in thesupply connection to each unit is adjusted so that relatively hightemperature at the discharge end of the unit, such as is present beforethe refrigerant is supplied to the unit, when expanded, will exert apressure on the diaphragm 72, tending to open the valve and permit freeow to the unit.

of eachunit is adapted to close the connec-l tion between the unit andthe return line under tensionv of the spring at the bottom of the valvewhich tension normally overbalances suction in the return line operatingon the valved diaphragm in opposition to the spring.

Under these conditions when the system isplaced in opera-tion,refrigerant flows to the severalfunits in the system, passes theautomatic back pressure and regulating Valve at the supply end of theunit, fills the coil,jand

is held in the coil because of the closure of' the valve at thedischarge end of the unit.A

When the coil is filled and pressure is built up therein to the properdegree, back pressure in the coil operates the back pressure valve andcuts ofi' the supply of refrigerant.

because of the interruption of the cooling action of the coil. When thetemperature has reached a sufficiently higlflimit, it acts on thethermostat 115 to close the electrical circuit to the heater,influencing the thermostat 107. When this circuit is closed, the heateris energized, the temperature of contents of the thermostat is raisedanda pressure built up in the upper chamber of the control valve 15,opening that valve so that flow to the return line is established,relieving pressure in the coil so that fresh refrigerant may bedelivered through the back pressure and regulating valve.

The cycle of refrigeration in the unit just described is then repeateduntil the temperatureof the compartmenthaslowered sufiiciently to effecta reverse operation of the thermostat 115, when the heater circuit isshut olf,`

contents of the thermostatic tube cools and the control valve 15 againcloses to shut ofi' the outlet and again build u a pressure in the coil,as beforel described. T is operation continues automatically while thesystem is in use, the supply of refrigerant being regulatedat the backpressure valve to provide the proper amount of refrigeration formaintaining the compartment at the desired and predeterminedtemperature.

The operation described in connection with one unit is repeated in eachof the other units, the only difference being in temperature which isdetermined by a setting of the individualback pressure valves.

It is apparent from the above that there will be a variation of ressurein the return line because of the di erent pressures under which theseveral units operate and the va` riable settings of the valves. As thecompartments to be kept at the lower temperatures `must have a freercirculation of refrigerant low temperature units; consequently dischargefrom one ofthe high temperature units to the return line would tend toflow in thedirection of thelower temperature units and interfere withrefrigeration in such units un- `less means were provided to preventsuch unit, they-tend to expand the diaphragm 91 in the valve of such lowtemperature unit and consequently close-'the valve to prevent flow ofsuch gases into the low temperature coil, thereby avoiding interferencewithy refrigerationtherein. Beingunableto escape into the lowtemperature coils, these gases are then conducted back to the compressorthrough the return line. Consequentlythe gases from any one of the unitsis not permitted to enter the coil of any of the other temperatureunits, the flow from the high temperature units being prevented bymechanical operation of the valves and iiow from a low temperature unitto a higher temperature Vunit being prevented by the higher pressuresinthe higher temperature units, and all of the units may operatesimultaneously at their dili'erent temperatures without interference onewith another. It has heretofore been statedthat thevalves 15 controllingdischarge from the units are setto normally close under tension oftheirv springs and are opened automatically through the thermostatcontrolledby tern-l perature in the compartment served by the units. Asmore rapid refrigeration can be effected by a freev flow of therefrigerant through the coil, it is desirable to open thev dischargewhen the system is first placed in operation so that the refrigerant mayflow freely through the coils to the return line. Inorder to effect thisopening and quick cooling of the compartments, I provide for Ans masterswitch 118 and automatic switch 117,

the automatic switchin turn being under control of thev thermostats 115in the several units. Consequently when the thermostatic switches 115are open during such periods after the compartments served by the unitsare at proper temperature, current is cut olf from the motor and thecompressor is idle. When, however, the temperature in the coin- Cellpartments served by any one of the cooling units rises above thecritical temperature and the therinostatic switch 115 is automaticallyoperated, closing the valve 15, it acts on the switch 117 to close thecircuit to the motor and the compressor is automatically started inoperation.

The above describes the normal operation of the system.

The refrigerant, in those compartments held at a temperature above thefreezing point, passing from the coil to the return line, is at atemperature below that of freezing, any moisture in the compartmentserved by the coil will settle on and frost the coil. Vhen the unit isautomatically cut oil through the thermostatic control, the liquid inthe coil in a compartment held at a temperature above the freezing pointrises in temperature to approach temperature of the compartment and whenit passes above the freezing point, tends to melt the frost and removethe frost incrustation.

As this automatic defrosting cannot ,take place in a compartment heldbelow the fieezing point, I provide manually controlled means foreffecting defrosting of such units. This manual control. includes theley-pass about the back pressure and regulating valves at the intake endof each coil, together with the valve controlling discharge from theunit and which is normally under automatic control of the thermostat115. When it is desired to defrost one of the low temperature coils, Iopen the by-pass about the back pressure and regulating valves at theintake end of the coil and open the circuit tothe electrical heater 109so that the therin ostatic switch cannot effect opening of the dischargevalve. With the unit set in this way, liquid from the receiver 3 ispassed into the coil of the set unit and, being unable to pass' on tothe return line, accumulates in the coil. Being unable to expand andperform its normal refrigerating function and having entered the coil ata temperature of approximately 90?", it is apparent that this hightemperature acting on the incrustation on the coil will tend to melt thefrost and clean the surface.

It is further apparent that transfer of heat from the ammonia during thefrosting operation reduces temperature of the ammonia so, that when thedefrosting has been conipleted, the temperature of the ammonia in thelower portion of the coil has been lowered to a degree which will renderit eiective for refrigeration in the succeedingly lower temperatureunits in the system.

lle-frosting of any one of the units does not interfere with the normaloperation of the other units as the opening of the circuit local at anyof the units will not interfere nitii automatic opening` and closing ofthe circuit through the thermostatsat the other units.

It is apparent, therefore, that I have provided a refrigerating systemwherein independent units served by the system may operate to maintaindifferent temperatures in different compartments without interferenceone with the other, that such units are automatically controlled bylocal temperatures and that defrosting of the coils in highertemperature compartments is automatic and that in lower temperaturecompartments may be effected at will and without interference with theoperation of any of the other units.

l/Vhat I claim and desire to secure by Letters Patent is:

1. In a refrigerating system, a cooling unit, valve mechanismcontrolling return flow from said unit, thermostatic means controllingsaid valve mechanism, and an electrical heater controlling saidthermostatic means and automatically controlled by temperature of acompartment served by said unit.

2. In a refrigerating-system, a coolingi unit, valve mechanismcontrolling return flowfrom said unit, thermostatic means controllingsaid valve mechanism, an electrical heater controlling said thermostaticmeans and automatically controlled by temperature of a compartmentserved by said unit, and a manual switch in the heater circuit.

8. In a refrigerating system, a cooling unit having supply and dischargelines, valve mechanism controlling the supply line and controlled bytemperature in the discharge line, a by-pass about said valve mechanismwhereby the unit may be supplied independently of the suppl through thetemperature controlled valve, tliermostatic means for con trolling thedischarge line, normally inert means for heating said thermostaticmeans, and manually operable means controlling the heating means.

4. In a refrigerating system, supply and return lines, a cooling unithaving connections with said. lines, an automatic valve in the returnconnection, normally tending lto close said connection, a thermostatcomprising a container for expansible iiuid in coinmu'nication with thevalve-whereby the valve is controlled by temperature of fluid in saidcontainer, a heater for the container. and connection between thecontainer and heater whereby relation of the heater to the container isautomatically varied according to temperature of contents of thecontainer.

5. In a refrigerating system, in combination with supply and returnlines, a cooling unit having its opposite ends connected with saidlines, an automatic valve normally tending io obstruct discharge fromsaid unit to the return line, a thermostat controlling said valve, anelectrical heaterfor said thermostat and controlled thereby to varyheating relation of the lieaterto the thermostat according totemperature of the thermostat, a

thermostatic switch in the heater circuit con-l trolling the circuit bytemperature in a compartment served by said unit, and a manual switch insaid circuit. f

6. In a refrigerating system including a plurality of independentcooling units, each adapted for serving a separate compartment, andsupply and return lines having branches to said units, independent meansautomatically controlling discharge from each unit by temperature of thecompartment served by the unit, and means in each supply branchresponsive to pressure inthe supply branch and to temperature of therelated discharge branch automatically controlling supply of refrigerantto the units.

7. In a refrigerating system including a plurality of independentcooling units, each adapted for serving a separate compartment,

y and supply and return lines having branches to said units, independentmeans automatically controlling discharge from each unit by temperatureof the compartment served by the unit, and means in each supply branchfor controlling supply of refrigerant to the units including meansresponsive to pressure in the supply branch and means responsive totemperature of the discharge branch oit said unit.

In testimony WhereofI 'aflix my signature. JOHN F. HOFFMAN.

